Embedding X applications in Xsharp

It is now possible to embed any X application as a child widget within an
Xsharp application. In the screenshot below, this is done for both "gedit" (a
GNOME app) and "kcalc" (a KDE app) running as two children of the same Xsharp
main window. The functionality of embedding X applications is important
e.g. because the next version of WinForms will have
a HTML web browser control widget, and we will be able to provide this
by embedding an existing third-part Free Software web browser, therefore we
not need to write a web browser from scratch in C#.